The interference-fit processing and split-sleeve cold expansion processing were employed on the 7050-T7451 aluminum alloy joints and fatigue test of joints were carried out. The effects of the processing on fatigue life were compared and characteristics of fatigue fracture appearance were studied by scanning electron microscope.
The results show that the interference-fit bolted joints obtain longer fatigue life with interference of 0.08∼0.14mm, the longest with 0.11mm, and the fatigue life of split-sleeve cold expanded bolted joints increase with hole cold expansion of 3-5%'s growth. The maximum fatigue life is increased to 3 times that of the non- cold worked joints.
The fatigue crack fractography present the characteristics of mixed transgranular fracture and material of 7050-T7451 has toughness. Interference-fit and split-sleeve cold expansion processing can also strengthen the wall of hole and make fatigue crack source from the surface of structure, not the wall of the hole.
Split-sleeve cold expansion processing can be beneficial for increasing the fatigue life better.